Thieves known as “nighthawkers” are trespassing on English farms and protected sites and using metal detectors to dig for antiquities, reports the Guardian. Among the items that have been stolen in the growing epidemic are bronze axes, Roman coins, Saxon jewels, and other precious objects connected to British history.

English Heritage, an organization concerned about the extent of this activity, commissioned a study published today, which concludes that the scope of the problem is larger than had been previously known.

According to the study, more than 200 raids were reported between 1995 and 2008, a number which archaeologists believe is only a small amount of the whole. The report also found that only a handful of those cases have gone to court, and that in most of them, the thieves received only a warning or petty fine.

Not surprisingly, just 14 percent of landowners bother to report this type of crime, believing that thieves will be difficult to prosecute and their punishments too lax. Once artifacts have been removed from their original locations, it isalmost impossible to establish their provenance. Many items end upbeing sold on online auction sites such as eBay.

Police also say that the “nighthawkers” have formed networks, often online, to trade information about vulnerable sites.

“This is seen as a victimless crime,” said archaeologist Pete Wilson. “But we are all the victims, our history is being stolen.”